As subsea hydrocarbon production systems have evolved over time, certain challenges have become more problematic. One challenge is that subsea pipeline systems now cover greater areas, therefore the pipelines must traverse greater distances. Pipeline system designers would like to have greater flexibility to utilize various sizes and types of subsea pipeline, particularly as systems become larger and more complex. Another challenge is that certain subsea production fields necessitate subsea pipeline crossing difficult geographical formations, including canyons, scarps and rough terrain. In these situations, it would frequently be desirable to utilize a flexible and/or lighter weight pipe or conduit with a different diameter for at least a portion of the pipeline system.
A consideration which often limits the pipeline system designer's ability to design pipeline systems adapted to such challenges is the piggability of the lines in the systems. It would be desirable to have the ability to maintain and service subsea pipeline systems including transitions between various types of pipe as well as various pipe diameters. Many such systems with a larger variation of diameter are not piggable with current technology. It would be desirable to provide pig assemblies capable of addressing the aforementioned challenges with the current technology.